Novel matting agent and its use

ABSTRACT

A matting agent for plastic compositions comprising either a high molecular weight, gel-containing vinyl chloride polymer with a gel content of 10 to 99% by weight, a maximum mercury porosity of 0.2 cm 3  /g, a maximum plasticizer absorption of 15%, a particle size parameter d&#39; of 10 to 80 μm and a coefficient of uniformity n greater than 3, or a high molecular weight, gel containing copolymer of vinyl chloride and 1 to 40% by weight of comonomer with a gel content of 10 to 99% by weight, a maximum mercury porosity of 0.10 cm 3  /g, a maximum plasticizer absorption of 10%, a particle size parameter d&#39; of 10 to 80 μm and a coefficient of uniformity n greater than 3, plastic articles containing said matting agent and a method of imparting a matt to the surface of plastic articles.

PRIOR APPLICATION

This application is a division of U.S. patent application Ser. No.766,044 filed Aug. 15, 1985 now U.S. Pat. No. 4,914,154.

STATE OF THE ART

Plastic articles generally have glossy surfaces which is in many casesundesirable and accordingly, there have been a whole series ofpublications concerned with finding a solution to this problem,especially with producing a surface for the most varied types ofplastics articles that is matt and as uniform as possible. For example,processes have already been described for the production of matt filmsin which the calender run-out rollers are roughened and are supposed togive the film a matt appearance on one or both sides by embossing. Apartfrom the disadvantage that the surfaces of these tools, which are veryexpensive to obtain, often have to be after-treated as a result of wear,the matting obtained therewith can hardly be described as uniform,especially when the films are further treated at elevated temperatures,for example by deep drawing processes and the like. Even when used forother purposes, these films soon have glossy areas again as a result ofabrasion. In addition, the apparatus is arranged for a certain type offilm and any conversion of the calender for other films is verytime-consuming and therefore expensive.

Consequently, various attempts have already been made to obtain uniformmatting by altering the formulations and by using additives, for exampleprecipitated silica or other inorganic matting agents. However, suchadditions of inorganic matting agents often involve a detrimental changein the physical properties of the shaped articles produced therefrom,and the processing properties of the molding compositions modifiedthereby are in many cases altered in an undersirable way, or evenimpaired. This may become evident, for example, through increasedabrasion of the shaping tools or through the formation of coatingscales, and in many cases through the drastically reducedthermostability of the mixture.

To avoid these difficulties, the solution that was often adaptedconsisted of adding high molecular weight polyvinyl chloride (PVC) orhigh molecular weight copolymers of vinyl chloride (VC) to the plasticcompositions, especially to PVC compositions.

For example, DE-A 27 16 853 described a molding composition consistingof a mixture of two portions of vinyl chloride polymer having differentaverage molecular weights and which, when subjected to a roll-kneadingcalendering process, results in films having a rough matt surface.Shaped articles produced from such molding compositions by extrusion donot, however, have the desired effect of silk-matt surfaces, but theirsurfaces are more or less glossy and rough. In so far as the moldingcompositions described in the application are based on polyvinylchloride produced by emulsion polymerization, they are entirelyunsuitable, for example, for extrusion to form hollow articles.

DE-A 25 20 229 discloses a process for the manufacture of shapedarticles having a "frost and ice effect", according to which there isused, inter alia, a polyvinyl chloride that has a K value of 55 to 65,that is produced by the suspension polymerization method and thatcontains no or only a small amount of plasticizer. Mixed with thispolyvinyl chloride is another suspension polyvinyl chloride having a Kvalue of more than 65; the K values of the two polymers should differ byat least 10 units. The addition of chemical propellants and/or talcum issupposed to improve the desired effect. It was found that, without thelast-mentioned additives, the appreciable matting effect can be achievedonly by using sand-blasted molds to roughen the plastic surfaces.

According to CH-A 457 822, a mixture of polyvinyl chloride types whichare in a ratio by weight of 30:70 to 70:30 and the K values of whichdiffer by from 10 to 30 units is also supposed to achieve matting. Carehas to be taken that, when processing on a vulcanizing machine knownfrom the rubber industry, the relatively high molecular weight plasticis completely bound or gelled.

EP-A 104 433 describes a molding composition based on vinyl chloridepolymers and the extrusion processing thereof which composition consistsessentially of from 5 to 50% by weight of high molecular weight,optionally partially cross-linked vinyl chloride polymer that ismanufactured by the suspension process and whose soluble portion has a Kvalue of more than 90, and from 95 to 50% by weight of a vinyl chloridepolymer having a K value of from 55 to 65. This composition is used forthe manufacture of bottles and other hollow articles having a silk-mattsurface.

It has also been found that, when processing polyvinyl chlorideplastisols, a reduction in gloss sufficient to produce slight mattingeffects can be achieved, for example, by admixing relatively largeamounts of high molecular weight types of polyvinyl chloride producedaccording to the microsuspension process with pastes based on polyvinylchloride having low to medium average molecular weights. For example,Vinnol.sup.(R) P 90 E is suitable for this purpose (Vinnol is aregistered trade mark of Wacker-Chemie GmbH, Munich). The matting effectis adequate for various applications but is not yet up to the requiredstandard. In addition, a common feature of all the compositions andprocesses discussed above is that they are suitable for only oneparticular processing method, that is to say the plastisol process orthe extrusion process or the calendering process, and in many cases giverough surfaces and/or unsatisfactory and/or non-uniform matting.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a novel matting agent whichavoids the above-mentioned disadvantages and provides the possibility ofobtaining reproducible, uniform and pronounced matting with a definedroughness and without glossy areas by an addition polymer and largelyindependent of processing methods and of the recipes (for example theplasticiser content) without in practice impairing the mechanicalproperties, thermostability and chemical resistance.

It is another object of the invention to provide novel plastic articleswith a matted surface containing the said matting agent and to a novelmethod of imparting a matted surface to a plastic article.

These and other objects and advantages of the invention will becomeobvious from the following detailed description.

THE INVENTION

The novel matting agent of the invention for plastic compositions iscomprised of either a high molecular weight, gel-containing vinylchloride polymer or a high molecular weight, gel containing copolymer ofvinyl chloride and 1 to 40% by weight of comonomer with a gel content of10 to 99% by weight, a maximum mercury porosity of 0.2 cm³ /g, a maximumplasticizer absorption of 15%, a particle size parameter d' of 10 to 80μm and a coefficient of uniformity n greater than 3.

The said matting agent is especially suitable both for use in plasticcompositions that are used in hard or soft processing, for example forthe manufacture of films and other sheet-like articles, especially on acalender, and, for example, for the manufacture of extrudates as well asfor use in plastisols in which the advantage of an improvement in theviscosity is also apparent.

The advantageous effect of the high molecular weight vinyl chloridepolymer, especially the surprisingly good and uniform matting which caneven be increased during further processing, for example by deep-drawingprocesses, and the unforeseeable possibility of being able to use thematting agent both in hard formulations and soft or even plastisolformulations, can be achieved even with an extremely small addition offrom 1 to 50% by weight, based on the total weight of the polymers, thatis to say the matting agent and the matrix polymer. In the case ofthermoplastic processing for the manufacture of hard and soft products,preferably from 2 to 10% by weight are sufficient and in the case ofplastisol processing, preferably from 10 to 50% by weight aresufficient.

The gel content of the matting agent which is the residue which isinsoluble on extraction with boiling tetrahydrofuran in a Soxhletapparatus over a period of 48 hours is from 10 to 99% by weight,preferably over 25% by weight, especially from 40 to 90% by weight.Relatively high gel contents, for example over 50% by weight, givebetter matting and relatively low gel contents produce at least adistinct reduction in gloss. The matting agent has a very uniformgranulation, expressed as particle size parameter d' and coefficient ofuniformity n according to the Rosin-Rammler equation (see DIN 66 141 orVauck-Mueller, "Grundoperationen chemischer Verfahrenstechnik", 5thedition, Dresden, 1962, page 234). The parameter d' is preferably from10 to 80, especially from 30 to 70, μm, and the coefficient n ispreferably greater than 4. It has been found that, because of the highgel content, the indication of a K value would serve no purpose in thecharacterization of the matting agent.

The maximum porosity of the vinyl chloride polymer matting agent,measured as mercury porosity at pressures of up to 300 bar, ispreferably 0.15, especially 0.10 cm³ /g, and the maximum plasticizerabsorption according to DIN 53 417 (German Industrial Standards) is 15%,preferably 10%. The vinyl chloride copolymers with other monomerspreferably have a maximum mercury porosity of 0.15, more preferably 0.10and especially 0.05, cm³ /g and a maximum plasticizer absorption ofpreferably 10%, more preferably 7%.

In the vinyl chloride copolymers, the amount of additional comonomer is1 to 40% by weight, preferably 5 to 20% by weight, based on the totalamount of monomer. Example of suitable comonomers are vinyl esters,preferably vinyl acetate and/or vinyl propionate; methacrylic andacrylic acid esters, preferably butyl acrylate and/or methylmethacrylate; maleic acid esters; fumaric acid esters and similarcopolymerizable monomers without other functional groups which are ableto cross-link the polymers.

The matting agent can be used together with customary vinyl chloridepolymers that are manufactured by the suspension, emulsion,microsuspension or block polymerization process and which are herereferred to as the matrix polymer. Depending on the processing method,the matrix polymer preferably has a K value of from 50 to 85. Often itis even possible to use matrix polymers having K values of up to 100. Itshould be noted, however, that when using matrix polymers havingrelatively high K values, better matting is achieved the greater the gelcontent in the matting agent. Matrix polymers having K values ofpreferably from 50 to 80, especially less than 70, can be usedespecially advantageously in hard processing and those having K valuesof preferably from 60 to 85, especially from 65 to 80, are especiallysuitable for soft processing and paste processing. Polymers having thehigher K values mentioned can also be used for the latter purpose.

Since formulations for the hard, soft and plastisol processing of vinylchloride polymers are generally known, it is unnecessary to repeat themhere. The few formulations that may be unsuitable will be recognized assuch and excluded by the person skilled in the art at the latest aftercarrying out a few preliminary tests. It should merely be mentioned thatthe customary additives can of course also be used concomitantlyaccording to the invention especially plasticizers, for example based ondicarboxylic acid esters and phosphoric acid esters, light and heatstabilizers, for example based on Zn, Cd, Ba, Pb and Sn, processingauxiliaries, for example lubricants based, for example, on acrylates,impact-resistance modifiers, for example based on ethylene; vinylacetate; acrylate or ethylene-vinyl acetate-vinyl chloride copolymers orgraft copolymers and ABS and MBS (see DIN 7728). Pigments and/or fillersmay also be included. A list of suitable additives can be found, forexample, in EP-A 104 433. These additives can be used in the customaryamounts.

The matting agent of the invention can of course also be used inconjunction with matting agents known hitherto, but also for example inconjunction with the mentioned Vinnol.sup.(R) P 90 E which, when usedalone, does not produce any real matting but, in reality, only reducesgloss.

The high molecular weight vinyl chloride polymer used in the inventionas a matting agent can be manufactured by the block (mass) or suspensionpolymerization process by copolymerizing vinyl chloride withcross-linking agents such as diallyl phthalate or maleate, triallylisocyanurate, diallyl ether, divinyl compounds, or di- and tri-acrylatesor methacrylates of polyhydric alcohols. The amount of cross-linkingagent is chosen by one skilled in the art so that the desired gelcontent of the polymer is obtained. The desired particle morphology canbe achieved in accordance with the processes of British Patent No.1164008; U.S. Pat. No. 3,813,373; and EP-A 28,812. According to thesecond embodiment of the invention the high molecular vinyl chloridepolymer can be manufactured as above with the modification, thatadditional monomers copolymerizable with vinyl chloride areconcomitantly used, said monomers being selected from the groupconsisting of vinyl esters, preferably vinyl acetate and/or vinylpropionate, esters of (meth) acrylic acids such as preferably butylacrylate and/or methyl methacrylate, esters of maleic and fumaric acidsand similar copolymerizable compounds having no additional functionalgroups and mixtures thereof.

Even with as low a content of matting agent as 1 to 50% by weight,especially in the case of thermoplastic processing from 2 to 10% byweight and in the case of plastisol processing from 10 to 50% by weight,based on the total polymer content, the plastic compositions of theinvention exhibit good to very good matting, which can even beincreased, for example by stretching, with a very uniform surfacestructure which corresponds, for example, to that which can be obtainedwith freshly sand-blasted calender rollers.

Even when subjected to shearing and relatively high processingtemperatures, the matting agent of the invention does not disintegrateinto its primary particles as do the hitherto customary plastic basedmatting agents which are manufactured by emulsion, microsuspension and,in some cases, also by suspension polymerization, and the matting agentof the invention thus ensures matting even in hard polyvinyl chlorideproducts. If primary particles are formed as a result of thedisintegration of the secondary structure of a matting agent then,because of the fineness, it is possible to obtain only a reduction ingloss and not a uniformly matt surface.

Although high molecular weight suspension polyvinyl chloride having acustomary particle structure has a matting action, the effect that canbe obtained depends to a very great extent on the processing method andthe formulation, for example the plasticizer content. If the secondarystructures are retained, this results in a very rough or non-uniformsurface and in a distinct deterioration in the mechanical properties,for example a reduction in the elongation at tear and in the tearpropagation resistance. In the case of a relatively high degree ofshearing and relatively high processing temperatures, the secondarystructures disintegrate to an increasing extent in these conventionalS-polyvinyl chloride products too whereby, again, the surface becomesvery non-uniform or even smooth. Even the cross-linking of suchS-polyvinyl chloride products only partially eliminates thesedisadvantages.

In contrast, the matting agents of the invention and the plasticcompositions manufactured therewith give reproducibly uniform surfacematting with a uniform defined roughness when using the most variedprocessing methods and conditions, in the case of hard, soft and pasteprocessing, without any appreciable impairment of the mechanicalproperties, thermostability and chemical resistance. In the case ofpaste processing, an advantageous reduction in viscosity is also broughtabout.

The plastic compositions of the invention are based on a vinyl chloridepolymer for the manufacture of shaped articles, sheet-like articles,coverings or coatings having a silk-matt surface which compositioncomprises a matrix polymer, from 1 to 50% by weight of a matting agentaccording to the present invention, based on the total weight of thepolymers used, of a high molecular weight vinyl chloride polymer and,optionally, other additives.

In the following examples there are described several preferredembodiments to illustrate the invention. However, it is to be understoodthat the invention is not intended to be limited to the specificembodiments. The K values were determined by DIN 53,726.

In the examples, the suitability of matting agents of the invention andnot of the invention for various methods of processing polyvinylchloride compositions was investigated. The matting agents were includedin the following basic formulations: in the zero formulation without amatting agent, 100 parts by weight of the matrix polymer or of themixture of the matrix polymers were used in each case.

Hard processing

1. Basic formulation for film calendering

95 parts by weight of Vinnol.sup.(R) Y 60 MS (mass Polyvinyl chloridehaving a K value of 60, Wacker-Chemie GmbH Munich)

5 parts by weight of matting agent

1.3 parts by weight of sulfur-tin stabilizer

0.5 parts by weight of glycerine monooleate

0.3 parts by weight of montanic acid ester wax

2 parts by weight of titanium dioxide pigment

Pre-plasticizing

variant I batch-wise with roll mill, 5 minutes at 165° C.

variant II continuously with single-screw extruder, temperature ofcomposition on discharge from die 175° C.

Film manufacture on L-shaped 4-roll calender, film draw-off ratio 1:1.15and 1:2.5

2. Basic formulation for sheet die film-extrusion

50 parts by weight of Vinnol.sup.(R) E 60 RN (emulsion polyvinylchloride having a K value of 60, Wacker-Chemie GmbH, Munich) and

45 parts by weight of Vinnol.sup.(R) H 10/60 (suspension PVCA having a Kvalue of 60, 10% of vinyl acetate content, Wacker-Chemie GmbH, Munich)

5 parts by weight of matting agent

2.2 parts by weight of Ca-Zn stabilizer

5 parts by weight of epoxidized soya bean oil

0.5 parts by weight of commercially available combination lubricant,

0.2 part by weight of polyethylene wax

3 parts by weight of titanium dioxide pigment and yellow pigment

3. Basic formulation for bottle blowing

95 parts by weight of Vinnol.sup.(R) Y 57 M (mass polyvinyl chloridehaving a K value of 57, Wacker-Chemie GmbH, Munich)

5 parts by weight of matting agent

1.2 parts by weight of sulfur-tin stabilizer

8 parts by weight of MBS impact resistance modifier

0.8 parts by weight of combination lubricant

0.1 part by weight of polyethylene wax

4. Basic formulation for impact-resistant hard profiles (for example forwindow profiles)

50 parts by weight of Vinnol.sup.(R) K 510/68 (graft polymer of chlorideon ethylene-vinyl acetate copolymer, Wacker-Chemie GmbH, Munich), Kvalue 68)

45 parts by weight of Vinnol.sup.(R) H 65 D (S polyvinyl chloride havinga K value of 65, Wacker-Chemie GmbH, Munich)

5 parts by weight of matting agent

2.5 parts by weight of Ba-Cd stabilizer

0.5 part by weight of phosphite chelator

3 parts by weight of pigments+fillers

0.8 part by weight of lubricant

5. Basic formulation for thermoplastic soft processing (calender,extrusion, blowing extrusion)

90 parts by weight of Vinnol.sup.(R) H 70 DF (S-polyvinyl chloridehaving a K value of 70, with a particularly high plasticizer absorption)

10 parts by weight of matting agent

40 parts by weight of dioctyl phthalate (DOP, diethylhexyl phthalate),

2 parts by weight of Ba-Cd-Zn stabilizer, processing aids analogous tobasic formulation 1

6. Basic formulation for paste processing (surface coat for floorcoverings)

40 parts by weight of Vinnol.sup.(R) E 79 CS (emulsion polyvinylchloride having a K value of 79, Wacker-Chemie GmbH, Munich)

25 parts by weight of Vinnol.sup.(R) P 70 (microsuspension polyvinylchloride having a K value of 70, Wacker-Chemie GmbH, Munich)

35 parts by weight of matting agent

35 parts by weight of benzylbutyl phthalate (BBP)

7 parts by weight of dodecylbenzene

1 part by weight of tin stabilizer

There were used as matting agents or as comparison substances:

(a) polyvinyl chloride having a gel content of from 83 to 84%,manufactured according to DE-OS 1,645,668 with the addition of 0.4% byweight triallyl isocyanurate (TAC, % based on vinyl chloride)

(b) polyvinyl chloride having a gel content of approximately 53%,manufactured as (a), but with 0.2% by weight TAC

(c) polyvinyl chloride having a K value of 100, soluble incyclohexanone, manufactured by the microsuspension process

(d) polyvinyl chloride having a K value of from 78 to 79, manufacturedby the emulsion process Vinnol.sup.(R) E 78 G, Wacker Chemie GmbH,Munich)

(e) polyvinyl chloride manufactured analogously to (a) but without TACadditive

(f) S-polyvinyl chloride manufactured by a formulation for K value 70with the addition of 0.4% TAC, with a gel content of from 75 to 80%

(g) commercially available precipitated silica

(h) commercially available matting agent based on acrylate

(i) S-polyvinyl chloride having a K value of 100, still soluble.

The results of the tests are given in the following Table.

In the Table:

-=no matting action ascertained

0=reduction in gloss

+=uniform matting

x=irregular specked surface

In the following tables examples according to this invention arenumbered and comparison tests are indicated by upper case letters.

    __________________________________________________________________________    Processing of rigid articles                                                          Matting agent           Bottle-                                       Example or comparison                                                                         calender process                                                                              blowing                                                                            Profile                                  Comparison test                                                                       agent   Variant I                                                                          Variant II                                                                          Extruded                                                                           film extrusion                                __________________________________________________________________________    1       a       +    +     +    +    +                                        2       b       0    +     +    +    +                                        3       a + 5 Parts                                                                           +    +                                                                by wgt.                                                                       Vinnol ®                                                                  P 90 E                                                                A       none    --   --    --   --   --                                       B       c       0    0                                                        C       d       -    -     0                                                  F       e       -    -     -                                                  E       f       x    x                                                        F       g       x    x                                                        G       h       g    +                                                        H       i       0          x    x    x                                        __________________________________________________________________________

    ______________________________________                                        Processing of soft articles                                                   Example                                                                       Comparison                                                                             calender films Blown   Extruded                                      test     Variant I                                                                              Variant II                                                                              films articles                                                                             Pastes                               ______________________________________                                        1        +        +         +     +      +                                    2        0        +         +     +      +                                    A        -        -         -     -      -                                    B        0                        0      0                                    C        -        -                                                           D                                                                             E                                                                             F                                                                             G        x        x         x     x      x                                    H        x        x         x     x      x                                    ______________________________________                                    

Examples 1 to 3 were repeated using as the matting agent (A) a copolymerof 86% by weight of vinyl chloride and 14% by weight of vinyl acetatewith a gel content of 56 to 57% produced by DE-OS 1,645,668 containing0.5% by weight of TAC based on the copolymer and (B) a copolymer of 85%by weight of vinyl chloride and 15% by weight of vinyl acetate with agel content of 66 to 67% produced by DE-OS 1,645,668 containing 0.3% byweight of TAC. The results were the same as in Examples 1 to 3 exceptthat in Example 2 using the (B) copolymer, variations I of both hard andsoft processing also showed uniform matting.

Various modifications of the matting agent and the plastic compositionsand the method may be made without departing from the spirit or scopethereof and it should be understood that the invention is intended to belimited only as defined in the appended claims.

What we claim is:
 1. A matting agent which is a high molecular weight, gel containing copolymer of vinyl chloride and 1 to 40% by weight of comonomer with a gel content of 10 to 99% by weight, a maximum mercury porosity of 0.10 cm³ /g, a maximum plasticizer absorption of 10%, a particle size parameter d' of 10 to 80 μm and a coefficient of uniformity n greater than
 3. 2. A matting agent of claim 1 wherein the mercury porosity is 0.10 cm³ /g.
 3. A matting agent of claim 1 wherein the mercury porosity is 0.05 cm³ /g.
 4. A matting agent of claim 1 wherein the maximum plasticizer absorption is 7%.
 5. A matting agent of claim 1 wherein the amount of comonomer is 5 to 20% by weight.
 6. A matting agent of claim 1 wherein the comonomer is at least one member of the group consisting of vinyl acetate and vinyl propionate.
 7. A plastic composition based on a vinyl chloride polymer for production of shaped articles, sheet-like articles and coatings with a silk-matt surface comprising a vinyl chloride matrix polymer, optional customary additives and a matting agent of claim
 1. 8. A composition of claim 7 wherein the matrix polymer has a K value of 50 to
 80. 9. A composition of claim 7 wherein the matrix polymer has a K value of 60 to
 85. 10. A method of imparting to articles made of a vinyl chloride matrix polymer a silk-matt surface comprising incorporating into the matrix polymer a sufficient amount of a matting agent of claim 1 to obtain silk matt surface.
 11. The method of claim 10 wherein the matrix polymer has a K value of 60 to 100 and is in the form of a plastisol.
 12. The method of claim 11 wherein the amount of matting agent is 10 to 50% by weight based on the total polymer. 